Print head mounting assembly

ABSTRACT

Improved means for releasably locking a typewriter ball-type print head to a driving head shaft are disclosed. The print head has a downwardly-projecting hub which is slidably received on the head shaft and is axially locked thereto by means of a springloaded locking pin which snaps out from its retracted position within the head shaft to rest on the top wall of the print head, the print head being axially releasable by operating a cam lever located on the print head top wall. A key pin extending from the head shaft engages a key slot at the lower edge of the hub when the print head is seated on the drive shaft to angularly lock the print head to the head shaft.

United States Patent [191 Miller PRINT HEAD MOUNTING ASSEMBLY [75] Inventor: Harry R. Miller, Trumansburg, NY. [73] Assignee: SCM Corporation, New York, NY.

[22] Filed: .Ian. 26, 1973 [21] Appl. No.: 326,622

[52] U.S. Cl. 197/52, 197/55 [51] Int. Cl B4lj l/60 [58] Field of Search. 197/52, 55; 292/246, DIG. 50;

[56] References Cited UNITED STATES PATENTS 2,905,302 9/1959 Hickcrson 1917/52 3,050,170 8/1962 Dodge ct al. 197/52 3,286,806 11/1966 Schoenfelder 197/52 X 3,432,018 3/1969 Watanabe et a1 197/55 X 3,618,735 11/1971 Bleau 197/55 3,645,372 2/1972 Noell et a1. 197/52 FOREIGN PATENTS OR APPLICATIONS 923,228 4/1963 Great Britain 197/52 656,971 1 /1963 Canada 197/52 1,063,612 8/1959 Germany l97/52 [111 3,826,345 July 30, 1974 OTHER PUBLICATIONS Spherical Type Element Holding Device," IBM Tech. Discl. Bulletin, Vol. 13, No. 1, June 1970.

Primary Examiner-J. Reed Fisher Assistant Examiner-E. H. Eickholt Attorney, Agent, or Firm-Kenneth W. Greb; Milton M. Wolson [57] ABSTRACT Improved means for releasably locking a typewriter ball-type print head to a driving head shaft are disprint head, the print head being axially releasable by operating a cam lever located on the print head top wall. A key pin extending from the head shaft engages a key slot at the lower edge of the hub when the print head is seated on the drive shaft to angularly lock the print head to the head shaft.

7 Claims, 5 Drawing Figures ee'e ooe

PRINT HEAD MOUNTING ASSEMBL BACKGROUND THE INVENTION in the form of a hollow truncated sphere or ellipsoid having the characters arranged in rows and columns on the outer surface thereof and are mounted axially on the supporting drive member. In operation, the printing head is selectively tilted and/or rotated thereby moving one of the characters to a printing position.

It is desirable that the means for mounting the print head to the supporting drive member provide a secure and reliable mounting connection while permitting easy release of the type head for replacement of the print head by another head with different characters. Presently known means for effective mounting of the print head usually require loop springs with extending arms and similar types of mechanisms which hav proven to be cumbersome.

BRIEF SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved character-by-character print head assembly providing secure mounting of the print head to the driving member providing easy release of the print head for replacement thereof by another print head of similar construction.

It is a further object of the present invention to pro vide a simply constructed character-by character print head assembly. I I

In accordance with the principles of the present invention there is provided a print head mounting assembly comprising a print head, a head shaft for receivably mounting the print head and releasable locking means on the head shaft for preventing axial and rotational movement of the print head with respect to the head shaft. The print head comprises a truncated spherical shell bearing printing characters formed on the exterior surface thereof, the shell. having a top wall with an opening therein and a hub extending downwardly from the opening into the interior of the shell. On the head shaft there is provided head seating means for axially supporting the hub, axial locking means for releasably axially locking the print head to the head shaft, and angular locking means for locking engagement with the hub to prevent rotational movement of the print hea with respect to the head shaft.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 .is an exploded perspective view of the print assembly partially broken away, and the print head and head shaft in partial cross-section to reveal the constructional detail of the print head and head shaft in the disassembled condition;

head shaft in the assembled condition, taken along the line 44 of FIG. 2; and

FIG. 5 is a perspective view of the print head assem bly mounted in a typewriter (shown schematically) in the operative condition.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, and in particular to FIGS. 1-3 thereof, a print head 10in the form of a truncated hollow hemispherical shell 12 is open at the lower end thereof to receive a mounting member in'the form of ahead shaft 40. Shell 12 is advantageously formed of lightweight tough resilient-material such as high-impact plastic material and bears raised printing characters arranged in rows and columns on the outer surface thereof.

Shell 12 is formed with a central integrally-formed hollow cylindrical hub 18 havinga central throughbore 20 which extends through the flat top-wall 14 of shell 12 having bore 20 extending therethrough. As shown in FIGS. 1 and 2 the hub 18 extends downward into the interior of shell 12 and terminates well short of the lower edge thereof. The hub 18, however, could extend beyond the shell 12. The hub 18 is provided at its bottom edge with a rounded open key slot 26 and a tapered chute 28 which is circumferentially spaced from 1 usual rocker 34 in which is journalled amotor driven pivot shaft 36. The rocker 34 is movable parallel to platen 43 for letter spacing between adjacent'characters. The head shaft 40, which serves as the mounting member for print head 10, is adapted to efficiently receive and removably mount print head 10, and in operation of the typewriter, the head. shaft 40 and the mounted head 10 are rotated rapidly to selectively locate type characters for printing upon paper 41 supported about the typewriter platen 43.

Closely adjacent the upper end of head shaft 40, there is formed a horizontal bore 42' which extends radially in head shaft .40. Mounted within bore 42 is a locking pin 46 and a spring 48 urging the pin 46 outwardly of the bore 42. The free end 50 of locking pin 46 is rounded and projects outwardly beyond the outer surface of head shaft 40 an amount determinedby a shoulder 51 of pin 46 abutting a wall 53 of head shaft 40. The pin 46 and the spring 48 are assembled into one end of the bore 42 and retained by a set screw 55.

A collar 54 is formed on the head shaft 40 and is located below the upper end thereof by a distance slightly greater than the height of hub 18. A cylindrical key pin 52 is secured to head shaft 40 and projects radially therefrom immediately above and resting upon the collar 54. I v

A raisedcircular cap portion 56 is mounted in the shell to'p'wall l4 by screws (not shown) threaded in holes 57 and S9 in the shell 12. Formed centrally in cap 56-is an elongated open cam slot 58 having parallel straight side walls and occupying most of one diameter of cap 56. At the rear portion of slot 58 there is pivotally and slidably mounted a cam lever 60 by means of cam shaft 62. The shaft 62 is journalled and guided in a pair of opposing horizontal grooves 44 (only one shown) formed in the side wallsof slot 58. Cam lever 60 functions as a handle while in the releasing upright position shown in FIG. 1 and permits locking the shell 12 to the'head shaft 40 while in the down closed position shown in FIG. 2. In-this closed position, cam lever 60 occupies'virtually all of cam slot 58 and its upper surface is flush with and forms a continuation with the curved upper surface of the cap 56. A finger piece 64 formed as an integral part of cam lever 60 is provided at the free endof cam lever 60 so that it can be raised to the upright position of FIG. '1. A detent 65 integrally formed across the underside of finger piece 64 engages a pair of stops 66 projecting laterally from the side walls of cam slot 58 for locking the cam lever 60 in the closed position shown in FIG. 2.

When print-head is to be inserted on head shaft 40, with cam lever 60 serving as a handle for print head 10 extended in the upright position, the open bottom end of hub 18 is centered over the top of head shaft 40 a head shaft positioned in said central openingfo'r slidably receiving said print head;

. head seating means iocated on said head shaft for so that the tapered end of locking pin 46 engages tapered chute 28 and key pin 52 is in line with key slot 26. lnthis initial movement, the tapered chute 28 and then the interior side wall of hub 18 depresses the tapered end of pin 46 inwardly into horizontal bore 42. The internal diameter of hub 18 and the external diameter of shaft40 are suitably dimensioned so that print head 10 is slidably but snugly received by shaft 40.

Head 10 is further lowered until the upper end of head shaft 40 emerges through top wall opening 20 and locking pin 46 snaps out under the spring tension of compression spring 48 and rests on the top surface of top'wall 14, thereby locking print head 10 axially onto head shaft 40. At the same time key slot 26 seats on key pin 52 to rotationally lock print head 10 to head shaft 40 to further insure proper location of print head 10 with respect to the rotate-tilt mechanisms of the typewriter while the bottom edge of hub 18 rests on the top surface of collar 54. The key pin 52 is located circumferentially of head shaft 40 relative to the locking pin 46 to always position the locking pin 46 in the path of a cam surface 63 of cam lever 60 when the print head l0 isassernbled to the head shaft 40. Cam lever 60 is supporting said print head; locking means on said head shaft includinga spring loaded locking pin located closely adjacent an upper end of said head shaft and having a free end normally projecting radially from said head shaft and resting on said locking surface when said print head rests against said head seating means for locking said print head on said head shaft; and i cam lever having a cam portion mounted on said print head, said cam lever-being movable from a lower horizontal position to an elevated position,

said cam portion being positioned to engage the projecting free end of said locking pin and urge said locking pin longitudinally to a print head release position in response to movement of said cam lever to its elevated positionto permit removing said print head from said head shaft. 2. A print head mounting assembly as defined in claim 1 wherein said locking means includes said head shaft having a radial horizontal bore, a' spring and said locking pin positioned within said bore, said spring being operable for urging said locking pin outwardly of said bore.

3. A print head mounting assembly as defined in claim 1 wherein said print head supports a cap having means slidably and pivotably supporting said cam lever, which movement occurs when said cam lever moves between said horizontal and elevated positions.

4. A print head mounting'assembly as defined in claim 3 wherein said cap means is a pair of grooves.

5. A print head mounting assembly as defined in claim 4 wherein said cam lever has a shaft positioned in said grooves of said cap for slidably and pivotably supporting said cam lever.

I 6; A print head mounting assembly'as defined in claim 5 wherein said print head supports a cap having stop meansthereon, said cam lever having a detent for- 7. A print head mounting assembly as defined in claim 1 wherein said print head supports a cap having stop means thereon, said cam lever having a detent for engaging said stop means to releasably lock said cam lever in said horizontal position.

* k *k' =l= 

1. A print head mounting assembly comprising: a print head bearing printing characters, said print head having a central opening and having a locking surface; a head shaft positioned in said central opening for slidably receiving said print head; head seating means located on said head shaft for supporting said print head; locking means on said head shaft including a spring loaded locking pin located closely adjacent an upper end of said head shaft and having a free end normally projecting radially from said head shaft and resting on said locking surface when said print head rests against said head seating means for locking said print head on said head shaft; and a cam lever having a cam portion mounted on said print head, said cam lever being movable from a loweR horizontal position to an elevated position, said cam portion being positioned to engage the projecting free end of said locking pin and urge said locking pin longitudinally to a print head release position in response to movement of said cam lever to its elevated position to permit removing said print head from said head shaft.
 2. A print head mounting assembly as defined in claim 1 wherein said locking means includes said head shaft having a radial horizontal bore, a spring and said locking pin positioned within said bore, said spring being operable for urging said locking pin outwardly of said bore.
 3. A print head mounting assembly as defined in claim 1 wherein said print head supports a cap having means slidably and pivotably supporting said cam lever, which movement occurs when said cam lever moves between said horizontal and elevated positions.
 4. A print head mounting assembly as defined in claim 3 wherein said cap means is a pair of grooves.
 5. A print head mounting assembly as defined in claim 4 wherein said cam lever has a shaft positioned in said grooves of said cap for slidably and pivotably supporting said cam lever.
 6. A print head mounting assembly as defined in claim 5 wherein said print head supports a cap having stop means thereon, said cam lever having a detent for engaging said stop means to releasably lock said cam lever in said horizontal position.
 7. A print head mounting assembly as defined in claim 1 wherein said print head supports a cap having stop means thereon, said cam lever having a detent for engaging said stop means to releasably lock said cam lever in said horizontal position. 